Abstract
Semantic Web technologies are widely used for storing RDF data and making them available on the Web through SPARQL endpoints, queryable using the SPARQL query language. While the use of SPARQL endpoints is strongly supported by Semantic Web experts, it hinders broader use of RDF data by common Web users, engineers and developers unfamiliar with Semantic Web technologies, who normally rely on Web RESTful APIs for querying Web-available data and creating applications over them. To solve this problem, we have developed RAMOSE, a generic tool developed in Python to create REST APIs over SPARQL endpoints. Through the creation of source-specific textual configuration files, RAMOSE enables the querying of SPARQL endpoints via simple Web RESTful API calls that return either JSON or CSV-formatted data, thus hiding all the intrinsic complexities of SPARQL and RDF from common Web users. We provide evidence that the use of RAMOSE to provide REST API access to RDF data within OpenCitations triplestores is beneficial in terms of the number of queries made by external users of such RDF data using the RAMOSE API, compared with the direct access via the SPARQL endpoint. Our findings show the importance for suppliers of RDF data of having an alternative API access service, which enables its use by those with no (or little) experience in Semantic Web technologies and the SPARQL query language. RAMOSE can be used both to query any SPARQL endpoint and to query any other Web API, and thus it represents an easy generic technical solution for service providers who wish to create an API service to access Linked Data stored as RDF in a triplestore.
Highlights
While developed to solve the specific problem of providing Representational State Transfer (REST) Application Programming Interfaces (APIs) for OpenCitations data, C RAMOSE has been developed in a way which permits it to interact with any SPARQL endpoint, following the rationale we adopt for all our software development, namely: while addressing the problem at hand, do this in a manner that provides a generic, open and public tool which can be reused by others with similar requirements
Several tools, in particular REST APIs on top of SPARQL endpoints, have been developed to leverage RDF data served through SPARQL query interfaces, often employing bespoke solutions tailored to their data, such as the DBpedia REST APIs and the Europeana Search API
We have illustrated all the features that RAMOSE implements and we have presented the analysis of our motivating scenario, namely the dramatic increase in usage of OpenCitations data demonstrated by our access logs, to
Summary
Application Programming Interfaces (APIs) are powerful means of automating communication between application programs and data services. Within the Semantic Web domain, the SPARQL 1.1 specifications include a Recommendation for “an application protocol for the distributed updating and fetching of RDF graph content in a Graph Store via the mechanics of the Hypertext Transfer Protocol (HTTP)” [15] Such REST-based access to SPARQL endpoints has been a common ground used by several Semantic Web developers to query RDF data available on the Web [2]. R flexible mechanism to serve RDF data integrated with information belonging to non-RDF data providers To address such needs, we developed RAMOSE, the RESTful API Manager Over SPARQL Endpoints C RAMOSE has been developed in a way which permits it to interact with any SPARQL endpoint, following the rationale we adopt for all our software development (available at https://github.com/opencitations), namely: while addressing the problem at hand, do this in a manner that provides a generic, open and public tool which can be reused by others with similar requirements. After a discussion on other existing works concerning other software that addresses similar scenarios (Section 5), we conclude the article (Section 6) by sketching out some planned future developments
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